University of Massachusetts Boston

Department of Chemistry

Thesis Defense

A hybrid supercapacitor based on chemically modified manganese dioxide and active
carbon in alkaline electrolyte

Presented by Quan Li

for the MS in Chemistry

Advisor: Professor Deyang Qu

Wednesday, January 15, 2014 | 10–11 a.m.

Chemistry Conference Room | Science S01-0089

Bismuth doped manganese dioxide (chemically modified MnO2) has been synthetized through a co-precipitation method based on patents issued to Ford. The morphology of the chemically modified manganese dioxide has been characterized by XRD, SEM; the capacity and rate capability of the material has been investigated with the assistance of classical electrochemical methods. By doping with bismuth, chemically modified MnO2 reveals a longer cycle ability and higher capacity compared to the blank MnO2.

The hybrid supercapacitor based on chemically modified manganese dioxide and active carbon and an alkaline electrolyte was studied. Different cell set-ups for the supercapacitor were proposed. A lager working potential window and longer cell cycle life were gained by using chemically modified manganese dioxide as the positive electrode and active carbon as the negative electrode.

The cyclability of the cell was explored using parallel experiments designed to prove that the dissolution of Mn (III) is the critical factor affecting the cycle life of the cell. A sealed, starved electrolyte coin cell was employed in the cyclability test to reduce the dissolution of Mn (III). A better cycle life of up to 500 cycles was reached with 60% of original capacity remaining.

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